Effects of pre-anodizing and phosphates on energy consumption and corrosion performance of PEO coatings on AA6082

Abstract

A significant reduction in the energy consumption of Plasma Electrolytic Oxidation (PEO) coatings on AA6082 alloy was obtained using strategies based on electrolyte selection and a precursor anodic film. PEO coatings were developed on AA6082 in silicate-based electrolytes with different phosphate species without and with a precursor oxide layer. The electrical response and, therefore, the specific energy consumption depended on the phosphate species and most notably on the applied pretreatment. The best result was obtained after anodic pretreatment and PEO in silicate-polyphosphate electrolyte with a reduction up to ⁓66% in comparison with the most conventional treatment (direct PEO in orthophosphate electrolyte). The corrosion response is not affected significantly by the pre-anodizing treatment either for short or prolonged immersion times revealing that coatings synthesised under high-energy efficient conditions have comparable corrosion performance under aggressive corrosive environments compared to conventional PEO processes.